One of the oldest nightclubs in D.C. is getting an addendum.

The Eighteenth Street Lounge, a bar located at 1212 18th St. NW, is opening a bar within the existing bar Thursday, DCist reported. The cocktail bar will be aptly named Addendum because it is an addition to the former location and is neatly tucked away in the back of the lounge.

Addendum is replacing the old closed-off bar, formerly called Studio Bar. The 18-seat bar is furnished with velvet chairs and couches, intricate woodwork and subtle lighting which give the bar a cozy and intimate feel.

Addendum will be open every week on Thursdays from 7 p.m. to 1 a.m. and Fridays and Saturdays from 7 p.m. to 2 a.m.

J.D. Quioco, a veteran bartender at Eighteenth Street Lounge, Lukas B. Smith, a bartender for Cotton & Reed, and the resident mixologist at Eighteenth Street Lounge, Michael Barton, took the lead on the project.

While Eighteenth Street Lounge serves up everything from classic rail drinks to an extensive bottle service list, don’t expect the bartenders at Addendum to serve you a traditional cocktail or anything with syrups, citrus or sodas.

In lieu of traditional mixers, Addendum’s drinks will be made with vermouth, sherry, amari and other bitters. The drinks at Addendum will cost between $11 and $17 each, according to the bar’s website.

One new cocktail is the “Derby Hat,” a drink that’s meant to mimic taste like grapefruit juice using only Jeppson’s Malö, Drambuie 15 whisky liqueur and various fruity bitters.